This invention relates to current and/or voltage protectors for inserting into a connecting block.
Connecting blocks are used in telecommunications systems for providing electrical connection at central offices and other locations between incoming and outgoing cables and to provide a cross-connection capability. Such connecting blocks also normally include voltage and current limiting protection devices to prevent damage to the circuits connected to the block. (See, e.g., U.S. Pat. Nos. 4,171,857 and 4,283,103 issued to Forberg et al.)
The protectors usually include a voltage surge protector element, such as a gas tube, current limiting devices, such as positive temperature coefficient (PTC) resistors, a ground electrode, and some form of thermal overload protection which short circuits the protector to ground in the event that any heat generated by the protector becomes excessive. The elements are typically mounted on a printed circuit board. (See, e.g., U.S. Pat. No. 5,299,088 issued to Honl et al.) The thermal overload protection is usually triggered by the melting of one or more solder pellets which brings a ground contact into electrical contact with the electrodes of the surge element. (See also U.S. Pat. No. 5,248,953 issued to Honl and U.S. Pat. No. 4,642,723 issued to Achtnig et al.)
Such connectors perform satisfactorily. However, recently, connecting blocks have been proposed with short distances between adjacent contact pairs. (See, e.g., U.S. patent application of Conorich et al., Ser. No. 08/442,862, filed May 17, 1995, and assigned to the present assignee.) Such short distances require smaller protectors, which are difficult to achieve considering all the elements needed for such a protector.